Carbon nanotubes (CNTs) are excellent material for sensors due to their small form factor, high sensitivity, superior electrical properties and flexibility in adding sensitizing (functionalization) layers onto their surface. CNTs are essentially single sheets of graphene rolled into cylinders. They usually possess a single wall, double wall or multiple walls. The typical diameter is 0.4-10 nm and the length may vary from several nanometers to centimeters.
Carbon nanotube sensor devices have found several applications as chemical sensors and can detect analytes in gas phase and liquid phase. CNT based chemical sensors are essentially electrochemical sensors and can be used in either a resistor or a field effect transistor configuration. In order to selectively detect specific analytes the CNT sensors are functionalized.